A number of these acts affect interstate commerce, concerning which the United States Constitution says: "No state shall, without the consent of the Congress, lay any impost or duties on imports or exports, except what may be absolutely necessary for executing its inspection laws." By a series of judicial decisions it has been determined that a State has a right to enforce laws affecting interstate commerce when traffic in the articles thus modified or prohibited affects the public welfare. When it is necessary to have a police regulation to prevent fraud in the traffic of an article or for the purpose of guarding the public health or morals, police laws, so called, may be enacted and enforced. Around this general question there has waged a bitter controversy which has occupied some of the best legal minds and is one involving some difficulty. FERTILIZER CONTROL One of the first of the "control" measures to be enacted, and the one which has been most universally adopted by the several states, is the law requiring the manufacturer and dealer in commercial fertilizers to guarantee the percentage of the so-called essential fertilizing elements--nitrogen, phosphorus and potassium--contained in each bag of fertilizer offered for sale. Subsequent control laws have been modeled more or less closely after this law. Hence a description of the operation and execution of it will serve for all. The execution of this law is usually under the immediate supervision of the state secretary of agriculture, while the necessary chemical analyses are made by the state experiment station. In some states the enforcement of the law is in charge of the state experiment station, while in others the state department of agriculture has its own laboratories or employs a private chemist. It is, however, becoming a more and more settled policy to place all police regulations in charge of the state department of agriculture, while at the same time the chemical analyses and other scientific and technological inquiries are made at the state experiment station. In order to facilitate the taking of samples and in order to raise funds for the execution of the law, the manufacturer is required to take out a license and to make a statement of the brands of fertilizers which he will place upon the market in the given state during the given season.